Aux radiator fan cutting off when A/C is on

[bradleyheathhays]

96 XJ here. Should my radiator e-fan (auxiliary) be cutting off when my A/C is on? I thought it ran continuously when the A/C was on, but my e-fan cuts off when the compressor shuts off. It only runs when the compressor is running.

Is this normal, or should the aux fan be running continuously w the AC on?

Thanks.

 

[Jeepergeo]

Compressor on: aux fan on.
Compressor off, temp good: aux fan off.
Compressor off, temp high: aux fan on.

No sense running the aux e-fan when the load is low and/or the engine is running in spec. I suspect by default AC on is considered a load...though that might not make sense if it is cold out and the AC is being used to dehumidify.

 

[bradleyheathhays]

That's the thing, the engine doesn't seem to be running in spec. A little overheating is usual when outside temps are in the mid 90s, but this year it's been happening in the mid 80s with engine temp going way higher than previous years. It's gotten a smidge cooler now, so I'm not so pressed to figure it out, but I'm still wondering how I can prevent it.

Do thermostats ever fail to where the engine overheats? I always thought they failed where they stayed open too much, allowing for too much cooling.

 

[superj]

They can also fail closed

 

[bradleyheathhays]

Need to change that thing out right away then. It's too easy to get to not to eliminate the possibility. It's been a while since it was replaced anyway.

 

[JPNinPA]

Fill and burp your radiator and be sure there is some fluid in the expansion tank.? Then reassess.
Engine should run app 210 That it is 15 deg higher than the 195 thermostat. There are two temp sending sensors. One on the back of the engine that drives the gauges. Then one on the thermo housing that goes to the ECU.

If the thermo fails closed pressure will build and push more fluid into the expansion tank.
Most thermos fail open . Quick test is how long it takes to get up to 210. If it rises within a mile from a cold start and driving app 35 mph. That is good. If it takes 3-5 miles it is likely the thermo is failed open.

Also consider your cabin heater is part of your cooling system. It bypasses the thermo. So if it is vlogged there is no bypass and pressure rises snd heat rises too.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[bradleyheathhays]

Fill and burp your radiator and be sure there is some fluid in the expansion tank.? Then reassess.
Engine should run app 210 That it is 15 deg higher than the 195 thermostat. There are two temp sending sensors. One on the back of the engine that drives the gauges. Then one on the thermo housing that goes to the ECU.

If the thermo fails closed pressure will build and push more fluid into the expansion tank.
Most thermos fail open . Quick test is how long it takes to get up to 210. If it rises within a mile from a cold start and driving app 35 mph. That is good. If it takes 3-5 miles it is likely the thermo is failed open.

Also consider your cabin heater is part of your cooling system. It bypasses the thermo. So if it is vlogged there is no bypass and pressure rises snd heat rises too.


Never look down on anyone unless you are helping them up - Jesse Jackson

Yes I had an issue with my radiator cap letting air suck in so I recently replaced the cap, filled and burped the coolant system. Reservoir full with coolant. I think everything there is ok.

Did not know that I had two temp sensors though. Are they both the same part? The parts stores' drill-down menus don't give a choice for two different coolant temp sensors.

Another thing...I've just been told that my compressor shouldn't be running intermittently when the ac is on, that it should stay on continuously. Guy suggested I check my refrigerant levels. This sound right?

 

[superj]

Its supposed to turn off when your ac reaches a certain temp. If it runs non stop, it can ice over. But, its notnaupposed to click on and off really quickly.


You should have a temp sensor and temp sender. One tells the ecu the engine temp so the fan can be turned on and off and one tells the gague what to rear, if you have the actual temp gauge. If you dont, then it just clicks the red light on at a certain temp

 

[JPNinPA]

Low AC pressure can lead to the AC compressor cycling. Given how old the vehicle is id get it leak checked. At least be sure to have it pumped and refilled.


Never look down on anyone unless you are helping them up - Jesse Jackson